The present invention is concerned with a device for fastening a stripping tool, a blank separator tool or a similar tool which is fitted on an adjustable crossbar of a waste stripping or blank separation station within a sheet processing machine.
U.S. Pat. No. 4,248,370, whose disclosure is incorporated by reference thereto and which claims priority from German Application 28 15 797, discloses a fastening device for securing a tool on a crossbar of a waste stripping or blank separating station within a sheet processing machine. The device includes a rod-shaped tie bar provided with a headed end which receives a freely shifting support for the tool, a first and second guide, each being provided at least with one supporting surface slanting with regard to the axis of the tie bar and constructed to act jointly with two corresponding guide surfaces on a crossbar of the station. Tightening means provided on one end of the tie bar and designed to push the sliding components toward the headed end of the tie bar in order to bring about a variation in their contact pressure enabling the execution of three operations, which include fitting and dismantling the tool, shifting the tool, and locking of various components with regard to one another on the crossbar.
In waste stripping stations of a sheet processing machine, for instance a press for die-cutting board sheets designed as packages, the state of the art consists in placing the die-cut sheet over a matrix plate which has a variety of apertures which are situated exactly underneath the various offal or waste cut outs for the sheet. The waste is then to be separated from the sheet, since it is not to be part of the finished product. To accomplish this, the bits of waste are to be put in contact with the strippers, which have, for the purpose to act on the waste in such a way as to detach it completely from the sheet and to push or eject it through the corresponding apertures or openings in the matrix plate.
Up to now, several solutions have been proposed for fastening the various strippers opposite the corresponding bits of waste. For example, as disclosed in U.S. Pat. No. 3,784,070, which is incorporated by reference thereto and which claims priority from German Application P 21 58 907.1, the die-cut sheet arrives in a station which is designed for ejecting the waste from the die-cut sheet. The strippers are fitted so as to be shiftable on crossbars which are, themselves, shiftable on two frames situated above and below the matrix plate on which the die-cut sheet is to be laid in order to align the tools with the position of the waste that is to be removed from the die-cut sheet.
In this connection, it is to be pointed out that the sheet generally contains a great number of bits of waste to be ejected and that, consequently, the upper and lower frames are to be equipped with a correspondingly large number of stripping tools, which sometimes may be more than 100 tools.
According to the above-mentioned U.S. Pat. No. 4,248,370, there are two possibilities for relative shifting the tool to allow a positioning of the stripper pin exactly opposite the portion of waste to be removed. These are the shifting of the stripper support with regard to the two clamp-shaped guides and shifting the guides or clamps with regard to the crossbar. Attention is to be drawn to the fact that this method of fastening, which has the advantages of allowing by means of a single action on a screw head, a simultaneous achievement of two relative shifts has already simplified the positioning of the strippers referred to hereinabove. However, on account of the rather large number of strippers fitted in the stripper station, the positioning of the stripper remains fastidious, since the operator is compelled to screw in more or less every screw by means of a wrench, depending on whether he wants to carry out the three essential operations of fitting and dismantling, shifting and locking. The rate of tightening of the screw, as involved with the one or the other of the three operations, cannot be determined easily and exactly and absorbs much time, especially so with, say, about 100 stripping tools.
Another drawback might also be mentioned in this regard. For example, the fastening device is not easy to assemble to fit on the crossbar on account of the fact that the clamps are able to turn independently from one another on the tie bar and, thus, do not always have their supporting surface in parallelism with the guide surfaces of the crossbar, which causes their assembly to be awkward. The screw making up the tie bar might be insufficiently screwed in for locking if one of the clamps is misaligned. In the event a screw is not properly tightened with the clamp properly aligned, the clamp might slip off from the crossbar. The fitting and dismantling operations are almost always to be carried out by using both hands.
It might also happen that after being locked on the crossbar, the fastening device being skewed with regard to the lengthwise direction of the crossbar. When the machine operates, the vibrations have a tendency to realign the device which realignment will result in a diminished pre-stressing and to cause the device to drop, entailing serious damages on the installation.
It might also happen that the technician, hastily locking a great number of strippers, especially so on a high-performance machine, with excessive tightening of the screw of the fastening device and, therefore, cause the breakage of certain components. To avoid this hazard, the tightening strength applied must, therefore, be checked.